The disclosure of Japanese Patent Application No. 2000-127339 filed on Apr. 27, 2000 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
1. Field of the Invention
The invention relates to a fastening device for fastening two parts at a peripheral portion.
2. Description of Related Art
For example, an air cleaner apparatus for a vehicle is constituted by a case (first housing) having a first opening and an air inlet, a cap (second housing) having a second opening which is facing to the first opening and an air outlet, a filter element wherein a seal member is mounted to the outer peripheral portion and sandwiched at each of the peripheral portion of the case and the cap, and the like. By connecting the case and the cap, for example, with a hinge structure, at one side of the peripheral portion, they are integrated to be relatively turnable around the hinge. By placing one peripheral portion over the other with the filter element sandwiched therebetween to be in a state where the first opening and the second opening are closed each other, they are fastened at other side in the peripheral portion with a metal clamp or the like.
FIG. 21 shows an example of the above-mentioned fastening structure, for example, as described in Japanese Laid-Open Publication No. Hei 8-281033. In FIG. 21 a clamp 194 is mounted to a flange 192 provided to project toward the outer peripheral portion on top end of a case 190 so as to be turnable around the axis center vertical to the paper face. The clamp 194 is formed by bending a thin metal plate in the direction of its surface to be apart from the flange 192 at the intermediate part in the longitudinal direction and having an engaging potion 196 formed by bending further greatly to face to the flange 192 at the extreme end side on the opposite side to the turning axis center. When the case 190 and the cap 198 are fastened with such a clamp 194, these flanges 192, 200 are put together and the clamp 194 is turned to the left direction in the drawing and the engaging portion 196 is projected to the flange 200 by pressing an operating part 202 provided at the extreme end toward the cap 198.
However, in the fastening structure by means of the above-mentioned clamp 194, applied force F1 required for fastening is given by F1=(L2/L1)F2; where resisting force F2 is for the engaging portion 196 to go over an angular portion at the edge of the flange 200, and L2 which cannot be universally set is defined by thickness of the flanges 192, 200, and thickness of a filter element not shown in the drawing. Therefore, since L1 to L2 cannot be set that long in the engine room of a vehicle where a dead space is desirably diminished as much as possible, there has been a problem that workability is bad because assembly load cannot be reduced at the time of fastening. such a problem is not limited to the above-mentioned air cleaner fastening structure for a vehicle, and it possibly occurs similarly as long as fastening structure where two parts are laid one over-the other at their peripheral portion and fastened with a clamp or the like.
The invention has been accomplished against the background of the foregoing circumstances and its object is to provide a fastening structure capable of reducing assembly load with a simple constitution.
In an aspect of a fastening structure according to the invention to accomplish such an object, a first peripheral portion of a first part and a second peripheral portion of a second part are put together and pressed to each other, whereby the first part and the second part are fastened. This fastening structure includes a first engaging portion provided with a first sliding contact surface facing to the second peripheral portion side at the opposite side to the first part in relation to the second peripheral portion and extending to the second part from the first part, a second engaging portion provided to the fastening part so as to be engaged with the first engaging portion and be relatively turnable around the predetermined turning axis, a second sliding contact surface provided to the second engaging portion so as to come in contact with the first sliding contact surface in the engaged state of the fastening part with the first engaging portion wherein pressing force applied from the first sliding contact surface increases as the fastening part is turned around a predetermined turning axis in the fastening direction, a peripheral portion pressing surface provided to the fastening part so as to press the second peripheral portion toward the first peripheral portion based on the pressing force and an operating part provided to the fastening part at a predetermined interval from the turning axis in order to turn the second engaging part around the turning axis against the first engaging part in the predetermined turning axis direction.
In such a manner, when the first peripheral portion of the first part and the second peripheral portion of the second part are put together and the second engaging portion of the fastening part is engaged with the first engaging portion extending from the first part and then the second engaging portion is turned against the first engaging portion in the fastening direction by operating the operating part of the fastening part, pressing force according to the turning amount is applied to the second sliding contact surface from the first sliding contact surface facing to the side of the second peripheral portion and based on this pressing force the peripheral portion pressing surface of the fastening part presses the second peripheral portion toward the first peripheral portion, whereby the first peripheral portion and the second peripheral portion are fastened. At this time, the required force for turning the second engaging portion, that is, assembly load is smaller as a fulcrum-point of force-application distance from the turning axis center to the operating part in relation to a fulcrum-working point distance from the turning axis center to the peripheral portion pressing surface increases, however, the fulcrum-working point distance can be set small regardless of a thickness of the first peripheral portion and the second peripheral portion to such an extent that the torsional stress being applied to the fulcrum does not exceed the tolerable value. Therefore, a fastening structure capable of reducing the assembly load with a simple constitution can be obtained.